kicker

after discussing my motor situation with my advisor (tx skoolz) i have decided to give my 175 a chance. if it does blow i will be able to find a motor cheaper in the winter. with that decision made i think for peace of mind i should buy a kicker motor. so if she does blow i wont be stranded. plus i want one for trolling anyway. my boat already has a kicker bracket on it. i'm thinkin 9.9. do i need long shaft or short? any advice or leads will be greatly appreciated. tx